Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Description
Machine for making absorbent items
Technical Field
The present invention relates to a machine for making absorbent items.
In particular, the present invention is used in the production of disposable
nappies for babies or incontinence pads for adults, to which the this text
explicitly
refers.
Background Art
As is known, nappies or incontinence pads comprise an absorbent pad,
usually made of cellulose fibres enclosed in a soft outer element, consisting
on one
side of a permeable sheet of "non-woven fabric", and on the other side of an
impermeable sheet of polyethylene. The two sheets are joined to each other
along
the respective edges, which are suitably shaped and equipped with retaining
elastic
elements.
In prior art machines the single nappies or incontinence pads are obtained by
means of an operation for cutting into pieces a continuous strip of nappies or
incontinence pads which are adjacent to each other and still joined one after
another.
Relative to their longitudinal axis, the nappies or incontinence pads
comprise a front portion and a rear portion, where two fastening and closure
elements are usually fixed, said elements designed to guarantee correct and
stable
positioning of the item around the user's hips.
The fastening and closure elements are generally fed in pairs and applied on
the continuous strip of nappies or incontinence pads before the strip is
divided into
single nappies or incontinence pads.
Patent application B02007AO00431 by the same Applicant describes a
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machine for making absorbent items of the above-mentioned type.
Said machine comprises a conveyor for feeding the continuous strip of
absorbent items to the device for cutting it into the single absorbent items,
through
a fastening and closure element feed station.
Said elements are formed, arranged in pairs and applied by a unit whose
infeed is fed with a continuous web of elastomeric material.
Said unit comprises a cutting element comprising a pair of rollers rotating in
opposite directions which are substantially at a tangent to each other, being
designed to obtain from the continuous web a succession of pieces, forming
trapezoidal fastening elements, by means of a succession of cuts alternating
obliquely in opposite directions along the longitudinal axis of the web.
After that operation the web is separated into a continuous succession of
pieces which have a trapezoidal shape, with reference to their bases
alternately
rotated through 180 relative to each other.
Downstream of the cutting element there is a separating roller which spaces
out the pieces. For that purpose, the separating roller, substantially at a
tangent to
a roller of the above-mentioned pair of cutting roller, has a prismatic shape
and
each of its faces, at an angle to the adjacent faces, is equipped with a
suction seat
that is substantially rectangular and designed to receive and retain one of
the
pieces.
Each suction seat can also move with a reciprocating motion parallel with
the axis of the separating roller during the latter's rotation and in the
opposite
direction to the adjacent seats, between the position for receiving a piece
and a
second position, reached at a position in which it is at a tangent to a roller
for
forming pairs of fastening elements.
During the transfer between the separating roller infeed and outfeed, the
fastening elements consequently pass from the condition in which they are
aligned
in a single row to a condition in which they are aligned in two rows which are
offset relative to each other and consist of trapezoidal pieces arranged so
that the
larger bases of the pieces of one row are opposite the larger bases of the
pieces of
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the other row.
Finally, the feed unit comprises the above-mentioned roller for forming pairs
of fastening elements, which aligns transversally to their direction of feed
each
fastening element in one row with an adjacent fastening element in the second
row.
For that purpose, the pair forming roller comprises two drums which are
coaxial, each having a plurality of radial arms separated from each other by
equal
angles for using respective suction seats to pick up the fastening elements
from the
separating roller. During the transfer from the station for pick up from the
separating roller to the continuous strip feed line, two radial arms relative
to two
successive pieces which are part of each of the rows perform a relative
movement,
thus forming a pair aligned transversally to the direction of feed-
The trapezoidal fastening elements are then applied in pairs at their larger
bases and according to a predetermined pitch, to the continuous strip of
absorbent
items.
However, the fastening element feed unit of the type described limits the
operating speed of the machine to which it belongs.
This is firstly due to the extreme mechanical complexity of the roller for
forming the pairs of fastening elements.
Secondly, in particular at high operating speeds, during relative sliding,
transversal to their direction of feed, of the seats of the separating roller,
despite
its prismatic shape, there may be interference between the edges of the
trapezoidal
pieces, with the risk that they may become detached from the respective
supports.
Disclosure of the Invention
The present invention has for an aim to provide a method and a machine for
making absorbent items which are free of the disadvantages listed above with
reference to the prior art.
The present invention provides a method and a machine for making
absorbent items as described in one or more of the appended claims.
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Brief description of the drawings
The present invention is described below with reference to the
accompanying drawings, which illustrate a preferred, non-limiting embodiment,
in
which:
Figure 1 is a schematic perspective view of a machine for making absorbent
items according to the present invention;
Figure 2 is a plan view of an absorbent item made by the machine of Figure
1;
Figure 3 is a schematic front view of a detail of Figure 1;
Figures 4a, 4b, 4c, 4d, 4e are schematic views of several operating steps of
the machine of Figure 1.
Detailed Description of the Preferred Embodiments of the Invention
With reference to Figures 1 and 2, the numeral 1 denotes as a whole a
machine for making absorbent items 2, in particular disposable nappies or
incontinence pads which have a substantially rectangular shape and which, with
reference to the longitudinal axis A, comprise a first or front part 3 and a
second
or rear part 4, separated from each other by a central part 5 located between
inwardly curving stretches of the two longitudinal sides of the item 2.
The items 2 comprise an inner absorbent pad, usually made of cellulose
fibres enclosed in a soft outer element and formed on one side by a permeable
sheet of "non-woven fabric" and on the other side by an impermeable sheet of
polyethylene.
Along its waistband line each item 2 is also equipped with two fastening and
closure elements 6, or tabs, projecting from the sides of the body of the item
2.
More precisely, the elements 6 project from the rear part 4 of the item 2 and
are
designed, in practice, to be superposed on respective lateral zones of the
front part
3, for fastening the item 2 around the user's hips.
The elements 6 usually comprise pieces in sheet form, preferably of elastic
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material and have a surface partly covered with an adhesive substance, or
equipped with other rapid fastening means.
The machine 1 comprises a line 8 for feeding, in a predetermined direction
L, a continuous strip 7 of items 2 which are arranged one after another.
5 The feed line 8 extends horizontally along a conveyor 9 comprising a belt
looped around end rollers 10 (only one of which is illustrated), as far as a
cutting
station where a cutting element 11 separates the continuous strip 7 into the
single
items 2.
Along the conveyor 9, upstream of the cutting element 11, there is a station
12 for feeding the fastening elements 6 using a unit 13 comprising a plurality
of
rotary conveyors consisting of rollers with horizontal axes parallel with a
direction
T transversal to the direction L.
With reference also to Figures 3 and 4, the unit 13 comprises, at its upper
end, a device 14 for cutting pieces 15 which are intended to form the
fastening
elements 6, fed with a continuous web 16 of elastomeric material unwound from
a
reel, not illustrated.
The cutting device 14 comprises two rollers rotating in opposite directions
and operating in conjunction with each other. More precisely, it comprises an
upper, cutting roller 17, rotating in a clockwise direction, and a lower
roller 18,
rotating in an anti-clockwise direction, designed to convey the pieces 15.
The roller 17 has two diametrically opposed blades 19 arranged obliquely,
relative to the roller axis, in opposite directions to each other.
The conveyor roller 18 has a cylindrical surface with holes in it which are
connected to a suction source, for retaining the pieces 15 after they have
been
separated from the web 16.
Substantially at a tangent to the conveyor roller 18, from upstream to
downstream with reference to its direction of rotation, there are two rollers
20 and
21, both rotating in a clockwise direction, forming a separator device 22 for
forming respective successions of fastening elements 6.
The rollers 20 and 21 are in turn substantially at a tangent to a roller 23
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rotating in an anti-clockwise direction and forming a device 24 for forming
pairs
of pieces 15.
Finally, the numeral 25 denotes a roller, rotating in a clockwise direction,
which is substantially at a tangent to both the roller 23 and the conveyor 9
and
forming an accelerator device 26.
With reference also to Figures 4a, 4b, 4c, 4d, 4e, during its passage between
the roller 17, equipped with oblique blades 19, and the roller 18, the web 16
is
divided into pieces 15 having a trapezoidal shape which, retained by suction
on
the cylindrical surface of the roller 18, are alternated and angled in
opposite
directions to each other.
For greater clarity in the accompanying drawings the pieces with the larger
base towards the right are labelled 15a and the pieces with the larger base
towards
the left are labelled 15b.
The roller 20 and the roller 21, at tangents to the roller 18 at two transfer
positions respectively labelled 27 and 28, are substantially equal, rotate in
a
clockwise direction and have on their respective cylindrical surfaces a
plurality of
seats 29 and 30 separated from each other by equal angles according to a
predetermined pitch P.
Each seat 29, 30, designed to receive and retain by suction one of the
trapezoidal pieces 15, comprises a block 31 able to slide in a direction
parallel
with the axes of the rollers, controlled by actuator means not illustrated,
between
two limit positions.
More precisely, the blocks 31 relative to the roller 20 pick up, at the
position
27, the pieces 15a with the larger base towards the right, whilst the blocks
31
relative to the roller 21 pick up, at the position 28, the pieces 15b with the
larger
base towards the left.
Starting from the respective transfer positions 27 and 28, the blocks 31 slide
in opposite directions to each other during rotation of the rollers 20 and 21,
forming respective successions 32 and 33, each comprising pieces angled in the
same way and spaced out, parallel with the axes of the rollers, by a distance
whose
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length is less than the transversal dimensions of the strip 7.
The pair forming roller 23, rotating in an anti-clockwise direction, has on
its
outer cylindrical surface close to each of the two longitudinal ends a ring of
seats,
respectively labelled 34 and 35 from left to right, separated from each other
by
equal angles according to the pitch P and arranged so that each seat 34 is
axially
aligned with a seat 35, forming a pair labelled 36 with it.
During its rotation the roller 23 receives, relative to each pair 36 of seats
34,
35, first a piece 15a from the roller 20 and then a piece 15b from the roller
21,
forming a pair of pieces 15 separated by the above-mentioned distance whose
length is less than the transversal dimensions of the strip 7.
Downstream of the position where the roller 23 and the roller 21 are at a
tangent to each other, the pair of pieces 15 is transferred from the pair 36
of seats
34, 35 to a corresponding pair 37 of suction seats 38, 39 on the accelerator
roller
25.
Each pair 37 of seats 38, 39 is mounted on a radial rod 40, able to oscillate,
during rotation of the roller 25, on an axis parallel with the direction T,
controlled
by cam actuator means (not illustrated) of the known type and described in the
above-mentioned patent application B02007AO00431.
Consequently, at the pick-up position for a pair of pieces 15 the respective
suction seats 38, 39 of the roller 25 have the tangential velocity of the
roller 23,
whilst at the moment of transfer of the pieces 15 the tangential velocity of
the
suction seats 37 coincides with the strip 7 feed speed, with consequent
passage of
the pitch of the pairs of pieces 15 from the above-mentioned value P to a
value P 1,
coinciding with the pitch of the stretches of the strip 7 intended to form the
single
nappies or incontinence pads.
At the position where the roller 25 and the conveyor 9 are at a tangent to
each other, the fastening elements 6 are applied to each of said stretches of
the
strip 7.
In other words, the machine 1 described above allows items 2 to be made
according to a method in which the fastening and closure elements are obtained
by
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cutting the continuous web 16 without waste to obtain from the web 16 a first
set
and a second set of fastening and closure elements in which the elements from
the
first set are angled in the opposite direction to and are alternated with the
elements
from the second set. Then the cut web 16 is fed through the station 27, in
which
the elements from the first set are picked up, and through the station 28, in
which
the elements from the second set are picked up. The elements from the first
set are
then fed by the roller 20 along a first path starting from the station 27,
whilst the
elements from the second set are fed by the roller 21 along a second path,
separate
from the first, starting from the station 28. As they are fed along the first
path, the
elements from the first set are moved sideways in a first direction.
Simultaneously,
as they are fed along the second path, the elements from the second set are
moved
sideways in a second direction which is opposite to the first direction. Both
of the
movements are in a direction parallel with the axes of the rollers 20 and 21.
Then the elements from the first set and the second set are transferred
separately from the rollers 20 and 21 to the roller 23, which forms a shared
third
feed path for the fastening elements. On the roller 23, alongside each element
from the first set, a corresponding element from the second set is placed in a
synchronised fashion, spaced out from and angled in the opposite direction to
the
element from the first set. Moreover, on the drum 23, after placing the
elements
alongside each other, in each pair of elements positioned side by side, the
element
from the first set and the element from the second set are further spaced out
until
the reciprocal distance established along the waistband line is reached.
From the above description it is apparent how dividing the pieces 15
between the two rollers 20 and 21 according to their orientation and the
subsequent formation of the pairs on the roller 23 allows a significant
mechanical
simplification compared with prior art solutions and eliminates the above-
mentioned disadvantage relating to interference between the edges of the
trapezoidal pieces, with the risk that they will become detached from the
respective supports, during their transfer.
